The most popular and accepted theory about the expansion of the universe is that it is being driven by dark energy. However, the research team at the University of British Columbia, Canada, proposed a new theory of why the universe is accelerating at a rapid pace; that it is likely due to quantum fluctuations of vacuum energy.

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In 1998, scientists discovered that the universe is expanding. They observed a light coming from supernovae and found out that the exploding stars are running away from each other at a fast pace. Scientists then concluded that the universe is expanding at an accelerating rate.

The discovery led scientists to accept the theory that the universe is filled with dark energy, and this is the reason why stars are constantly moving away from each other.

But two popular theories - Einstein's theory of general relativity and quantum mechanics - have different explanations about the universe. Scientists have found that the quantum level cannot be defined by the general relativity.

Upon applying quantum mechanics to vacuum energy, a huge density of energy appears. Since the general relativity says that this energy has a strong gravitational force, the universe will likely to explode. However, the universe still exists and is still expanding.

In a new study published in Physical Review D, Qingdi Wang and his colleagues sought to find solutions to the problem and determine why previous models failed to notice that the universe is constantly moving.

The team used a large density of vacuum energy and viewed in on the quantum scale. Through this, they were able to demonstrate how space is fluctuating uncontrollably, contracting, and expanding over time. This led to the result that the universe is expanding at a high speed.

The result implies that introducing cosmological constant or dark energy is not needed to have negative pressure to explain why the universe is rapidly expanding, researchers noted.

Bill Unruh, the co-author of the study, says that they want to test local fluctuations in the expansion of the universe or the actual fluctuations of energy. However, further research is needed to determine what indirect test is required for the development of the theory.

Unruh explains that the expansion of the universe will continue "forever," and these vacuum fluctuations of energy will not end.